This invention relates to the sealing of plastic pouches and more particularly to the sealing of plastic pouches to enable visible detection of contamination in the seal after a sealing process has been completed.
A new pouch of interest to ITT Continental Baking Company for their Flavor Seal Program has been purchased. This new pouch is of interest because it does not utilize any adhesive between pouch laminates. Extractants resulting from the adhesives have represented a stumbling block towards obtaining FDA approval for all previous pouch designs. Packaging test runs conducted with the new pouch of plastic material, however, revealed an inability to visually detect seal contamination after normal pouch sealing operations. The new pouch material which is of greater thickness than previously employed pouch material hides the normal signs (blisters and wrinkles) of contamination in the seal area after the sealing operation. Packaging tests were performed with the Flex-Vac Model 69 and Sentinel Model 12-AS sealing bars. The new pouches were intentionally contaminated with liquid (sauce) and solid (meat fiber and vegetable) food components. Pressure was applied with the above sealers using a heated flat bar to the top contaminated seal area. The contamination spread within the seal area creating cold spots as a result of the lack of heat transfer in the contaminated portion of the seal. The unsealed portion of the seal remained visually indistinguishable from properly sealed portions of the seal area. Seal contamination detection by visual inspections was therefore not possible using a seal operation that previously had provided for visual detection with previous pouch material. The only known non-destructive seal detecting technique is by using an infrared scanner which costs over $60,000, which is prohibitive.